(Newser)
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An outbreak of swine flu in Mexico has left 60 people dead and hundreds of others infected, the BBC reports. The World Health Organization says the strain that killed at least 12 of the victims has the same genetic structure of the flu that sickened seven people in Texas and California, reports NBC News. All seven people have recovered. The strain is a new one, and its source remains unclear.

“It is a virus that mutated from pigs and then at some point was transmitted to humans,” said a Mexican health official. Schools have been closed in Mexico City, and officials are launching a vaccination campaign. "We are very, very concerned," said a WHO spokesman. "We have what appears to be a novel virus and it has spread from human to human."